Composite foundry core

ABSTRACT

A foundry core having a main larger part and a smaller auxiliary part is formed with the smaller preformed auxiliary part being integrally molded into the larger part to provide a rigid unitary one piece core.

United States Patent 11 1 Nishiyama et al.

COMPOSITE FOUNDRY CORE Inventors: Keizo Nishiyama, Handa; Takeo Assignee:

Filed:

Appl.

Hiraiwa, Aichi-ken; Kohshi lwata, Nagoya, all of Japan Kabushiki Kaisha Toyoda J idoshokki Seisakusho, Aichi-ken, Japan Sept; 7, 1971 Foreign Application Priority Data Sept 7, 1970 Japan 45/78320 US. Cl. 164/369, 164/230 Int. Cl.

Field of Search References Cited UNITED STATES PATENTS 9/1908 Gibney l64/230 FOREIGN PATENTS OR APPLICATIONS l0/l960 Great Britain 164/230 Primary Examiner-Robert D. Baldwin Assistant Examiner-john E. Roethel Aftorriey RichardC. Sughrue. Robert U. Sloan et al.

ABSTRACT A foundry core having a main larger part and a smaller auxiliary part is formed with the smaller preformed auxiliary part being integrally molded into the larger part to provide a rigid unitary one piece core 1 Claim, 7 Drawing Figures COMPOSITE FOUNDRY CORE This invention relates to a foundry composite core comprising a main or larger core part and at least an auxiliary or smaller core part attached thereto.

The composite core of the above kind is utilized in such cases where a unitary prepared core is difficult to manufacture and/or to disengage it from the molded castings. In most of such cases, at least a part of the core is independently and separately blow-in molded beforehand and then inserted into a mating recess or the like female reception part formed in the main core body and then fixedly glued together.

More specifically in the case of the core adapted, in combination with a main core part for molding the crankcase forming part, for a common cylinder cover of a four-cylinder internal combustion engine, at least a core section for molding an intermediate bearing part of the engine is assembled together therewith. This core section consists of a pair of symmetrical core elements which are separately blow-in molded and assembled together to form a unit. This unit is inserted in a receiving recess formed in the main core section and glued thereto so as to provide a core assembly.

In order to provide the possibility for said insertion of the bearing core section and gluing of the latter firmly to the main core section, the said bearing-corereceiving recess must be machined to a high precision degree and the tedious glueing job must be carried into effect by consuming much of skilled labor.

A frequent and substantial drawback encountered when transporting such composite cores resides in the disengagement of the bearing core section from the main core body when received mechanical shocks from outside. When the glued joints between the bearing core section and the main core body have been defectively prepared, the bearing core section may separate from position and become afloat in the molten metal in the course of casting. of the cylinder cover. In addition, the removal of casting fins formed on the products at such areas corresponding to the fitting gaps between the bearing core section and the main core body of the core assembly is highly tedious and time-consuming.

The main object of the present invention is to provide an improved composite core, capable obviating substantially various conventional drawbacks above referred to.

A further object of the present invention is to provide an improved pattern assembly for the manufacture of the improved composite core according to this invention.

A specific object of the present invention is to provide an improved composite core specifically adapted for the manufacture of a cylinder block of a multicylinder internal combustion engine, as well as an improved pattern assembly for the manufacture of the improved composite core.

These and further objects, features and advantages will become more apparent when read the following detailed description of the invention by reference of the accompanying drawings in which:

FIG. 1 is a perspective view of an embodiment of the composite core according to the present invention.

FIG. 2 is an axially sectional view thereof, being drawn, however, on a slightly reduced scale.

FIG. 3 is an enlarged and exploded perspective view of a core section as a part of the composite core shown in FIGS. 1 and 2, said core section being adapted for casting an intermediate bearing part ofa cylinder block casting.

FIG. 4 is a schematic perspective view of a pattern assembly adapted for use in the manufacture of the composite core shown in the foregoing.

FIGS. 5 and 6 are two separate cross-sections of the pattern assembly shown in FIG. 4, its upper pattern member being shown in FIG. 5 in its operational position to close and define the molding cavity of said assembly and being omitted to show in FIG. 6 only for simplicity of the drawing.

FIG. 7 is a similar view to FIG. 4, showing, however, a modified embodiment of the pattern assembly from the foregoing.

Referring now to FIGS. I and 2 of the accompanying drawings, the numeral 1 represents generally a first embodiment of the foundry core according to this inven tion. This core I has been designed, by way of example, for casting a cylinder block of a four-cylinder internal combustion engine. As seen, the core 1 comprises four substantially cylindrical projections 20, 2b, 2c and 2d, generally represented at 2, and a main or crankcaseforming section 3 made integral with each other. These substantially cylindrical projections 2a 2d are arranged in line with each other and have such shape and dimensions as to shape the cylinder bores of the cylinder cover casting in cooperation with a master mold, not shown, as will become more apparent as the description proceeds. The cylinder-bore shaping section, generally shown at 2, and the crankcase-forming section 3 is united into a rigid one piece providing a core main body 4 which is combined with an intermediate bearing-shaping core section 5 which is shown rather schematically in FIGS. 1 and 2, yet more specifically in FIG. 3.

With increase of the number of the cylinders of the engine, the number of the intermediate bearings will be increased correspondingly. In such case, the number of the core, sections must naturally be increased correspondingly, although not specifically shown.

Although in FIG. 2, the last core section 5 is shown only schematically in one piece, it consists of two symmetrical core elements 5a and 5b shown in FIG. 3 in somewhat separated position for better understanding. As may be supposed from FIG. 1, these core elements are glued together along their mating surfaces. The inner surfaces of the thus assembled bearing core 5 defining an intermediate bearing-shaping gap space 6. As seen from FIG. 3, the opposing inner surfaces of core elements 5a and 5b have been designed to shape the sides of the bearing part of a cylinder cover use of the core 1 and a master mold, not shown, cooperating therewith.

On the inside surface of core element 5a, there is formed with a cylindrical projection 30 adapted for tight engagement with a correspondingly shaped and dimensioned recess, not shown, formed on the inner surface of the mating core element 5b, when the both core elements are assembled together to provide a rigid unit, generally shown at 5 in FIGS. 1 and 2.

The bearing core unit 5 is formed with lateral projections 7 and 7', as may well be supposed from observation at FIGS. 1 and 3 for mounting the core unit 5 in position on the pattern, as will be more fully described hereinbelow by reference to FIGS. 4 and 5. Numeral 8 represents a runner only schematically and partially.

Next, referring to the mode of and an apparatus for the manufacture of the foundry core 1. In FIG. 5, the numeral 9 represents generally a model assembly which is positioned below a resin-coated sand supply source, preferably a hopper of a conventional core blowing machine, not shown, and comprises a plurality of metallic pattern members 10 16.

First pattern member 10 is practically a provisionally stationary metal block and formed with a plurality of, four in this preferred embodiment, vertical bores 17 arranged along an axial line. At both ends of this block, there are formed with respective lateral shoulders 10a and 10b. The lower ends of the bores 17 are opened, but normally closed by a detachable closure strip 31, although its attaching and detaching means, preferably bolts-and-nuts, have been omitted from the drawing only for simplicity. In practice, the first pattern member is arranged vertically movable from a certain lower off-service position to its operating position shown in FIG. 5, although its guide means and drive motor such as a pneumatically or hydraulically operated pistoncylinder unit have been omitted from the drawing on account of their very popularity. Preferably, the cylinder of the unit is designed to be stationary, while the piston is mechanically connected with the pattern member 10 through a piston rod, not shown. This sliding movability is hinted by a double-headed arrow A".

First pattern member 10 is formed with an axially extending shallow cavity 18 adapted for shaping the shoulder parts 3a and 3b on the main section 3.

Second and third pattern members 11 and 12 are arranged to be slidable horizontally by respective pneumatic or hydraulic motors, not shown, as hinted by respective arrows 8" and C", so as to cooperate with the first pattern 10 for defining jointly a mold cavity. On the inside surface 110 of second pattern member 11, there is provided with a complexedly undulated surface 19 so as to correspond to an end-bearing forming surface 4a of the foundry core 1. Although not shown, third pattern member 12 is also formed on its inside surface with a similar undulated end-bearing shaping surface.

At the rear side of the pattern, there are provided two overlappingly arranged fourth and fifth pattern members 13 and 14 which are arranged to be independently slidable in the direction of a common arrow D by means of respective pneumatic or hydraulic pistoncylinder units, not shown.

A front or sixth pattern member 15 is movable in the direction of an arrow E" by a pneumatic or hydraulic motor as before.

At an intermediate point between the both ends, the fifth pattern member 14 is formed with a recess 20. In the similar way, sixth pattern member is formed with a recess 120. These recesses and 120 are adapted for receiving respectively the lateral projections 7. and 7 of an assembled bearing core section 5, so as to properly position the latter in the moldable cavity of the pattern unit when assembled together as will be more specifically described hereinafter. As seen most clearly in FIG. 6, pattern members 13 and 15 are formed with inwardly projecting runner-forming bars 21 and 121, respectively. These bars 21 and 121 are so designed and dimensioned, jointly to form the runner 8 in the foundry core 1 during manufacture thereof.

Fourth pattern member 13 is formed with an innerwardly projecting, horizontally extending bar adapted for shaping a corresponding runner part, not appearing in FIGS. 1 and 2.

Seventh or upper pattern member is shown generally at 16 in FIG. 4 and provided rigidly with a pair of mandrel roots 24a and 24b, so as to shape the hollow inside spaces 23a and 23b in the core 1, respectively. A number of material-blow-in holes, designated by a common reference numeral 25, are formed through the platelike base portion 16a of the upper member 16 which is movable from its upper off-service position to its lower operating position by means of a pneumatic or hydraulic piston-cylinder unit, not shown. This off-service position can substantially be assumed to be that shown in FIG. 4, when seen FIGS. 4 and 5 jointly. The operative position of the upper pattern member 16 relative to other members 10, l3, l4 and 15 may most clearly be seen from FIG. 5. Each two mandrels, designated by common numeral 124 depend rigidly from the root 24a or 24b, respectively. Material-blow-in holes 25 are connected with the material supply source, not shown. Naturally, the mandrels 124 are arranged concentrically with the vertical bores 17, although the upper pattern member 16 is shown in FIG. 4 as somewhat laterally offset in this position relative to that of the remaining pattern members shown therein.

In order to prepare the shell core unit 1 shown in FIG. 1, all the pattern members 10 16 are positioned in their off-service position and they are throughly and carefully cleaned in advance, so as to remove dirty substance occasionally depositted on the working or inner surfaces of these members which are then sprayed with a solution of conventional parting agent such as silicon resin, polyvinyl alcohol, paraffin or the like.

Then, the first or lower pattern member 10 is pneumatically or hydraulically elevated in its position from below to its upper operating one shown in FIG. 4. Next, second and third pattern members 11 and 12 are brought to their working position shown in FIG. 4 so as to snugly engage with the shoulders 10a and 10b on the first member 10.

Further, front pattern member 15 and rear pattern members 13 and 14 are advanced towards the pattern center, yet the upper rear member 13 is at its somewhat receded position relative to the lower rear member 14 as shown in FIG. 4. Then, the intermediate core section 5 held in its inverted position is brought into position with its lateral projection 7 and 7 kept in mating engagement with recesses 20 and 120, respectively. Further, the once receded member 13 is advanced to its final operating position. Finally, the upper pattern member 16 is lowered towards the pattern center so as to occupy its final operating position. The relative position of these pattern elements 10 16 and with each other and with the core section 5 will be most clearly seen from observation of FIGS. 5 and 6, thus the pattembeing closed completely. It should be mentioned, however, that in FIG. 6, the upper pattern member 16 has not yet been brought into its pattern closing position.

The core section 5 consisting of a pair of opposing core elements 5a and 5b has been preparatorily and separately prepared by the conventional shell core preparation process by use of proper molds and on a conventional core blowing machine. In practice, however, each of the core element 5a or 5b represents a concave outer side surface as clearly seen in FIG. 3 at 5', although in FIGS. 1 and 4, these outer surfaces are drawn into plane surfaces only for simplicity of the drawing. The bottom surfaces of these core elements 5a and 5b appear at top of the up-and-down inverted core section 5, as shown at 5" in FIGS. 4 and 6. The inverted core section position within the closed pattern unit comprising said members 16, especially by the mutual engagement between at 7 and 20; 7 and 120, respectively, and by the additional tight contact between the lower surface of fourth pattern member 13 and the now upper top surfaces 5" of the core elements 5a and 5b.

The preparatory pattern preparation and setting job including the insertion of core section 5 in position will consume, as an example, only about 30 seconds.

Means for holding the core section 5 in position may take a different form. In FIG. 7, an alternative of such positioning means is shown. A pair of tapered positioning pins 26 are fixedly studded on the upper surface of the first pattern member 10 and within the scoper of cavity 18. In this case, core elements 5a and 5b are formed with respective reception female openings, not shown, for snugly receiving these positioning pins 20.

After blow-forming of the core unit 1 to be described, the positioning lateral projections 7; 7' or positioning female openings said above can easily be cutout or filled-in by a simplest job, so as to provide a complete and defectless core unit 1.

With the pattern members 10, 14 and brought to their operating position to close the pattern or model unit 9 as shown in FIGS. 5 and 6, the molding or casting Space 6 is tightly closed by contacting these pattern members 10, 14 and 15 with the outline-defining parts of the core section 5, thereby assuring the shell-forming material to be described from invasion into said space 6 during the shell-core forming step to be described.

In the embodiment adapted for attaining a more effective seal against the space 6 and shown in FIG. 6, an inner and lower part of fifth pattern member 14 which is to be kept in pressure engagement with defining a corresponding part of the outline of said space 6, is made an independently movable member consisting of an heat-insulating plate 27, a buffer and backing plate 28 made of asbestos or the like'heat-resistant fibrous material, and a piston-like member 128 rigidly united with each other and mechanically connected with a pneumatic or hydraulicpiston-and-cylinder unit, not shown. This covering unit consisting of the aforementioned parts 27, 28, 1 28 and 129 is slidably received in a recess 14a formed in the fifth pattern member 14 as shown, and kept in pressure contact in its operating position shown in FIG. 6 with the right-hand side of the core section 5.

At the left-hand side of core section 5, there is a similar, yet opposingly acting covering unit which consists of similar party 27', 28', 128' and 120' and substantially received movably in a corresponding recess 15a formed in the front pattern member 15. The parts 27', 28', 128' and 129 correspond substantially to those which have been designated 27, 28, 128 and 129 respectively in the foregoing.

Upon the closure of the pattern unit 9 in the above mentioned way, the shell-forming material is blown from the supply source, preferably a hopper, not shown, positioned at a certain higher level, through the holes 25 into the molding cavity defined by the inner operating surfaces of the pattern members 10 I6.

An example of the material is in its composition as follows: siliceous sand:

phenolic resin hardening agent hexamethylenetetramine dispersing agent calcium stearate 2.5 wt. of said sand;

l5 wt. of said binder;

0.l wt. of said sand.

The blow-in pressure amounted to about 3 kglcm Upon finishing the blow-in molding the core unit 1 within the inside cavity of the pattern assembly 9, a baking step is carried out at 250 300C. The blow-in and baking steps extend for about seconds. For the baking purpose, these pattern members 10 16 are fitted with electric resistance means arranged within the interior of each thereof, although not shown by virtue of the very popularity. These heating means are preferably formed into resistance coils, totally of 54 killowatts, as an example.

Upon finishing this baking step, the pattern assembly is dismantled by energizing the respective pneumatic or hydraulic piston-cylinder units, not shown, for receding the members 10 16 from their operating to their offservice position so as to open the molding cavity. Then, the shell core unit 1 having the intermediate core section 5 rigidly embedded therein and baked together effectively in non-detachable way, is taken out from the opened pattern assembly. For increasing the rigid and baked combination of the core section 5 with main core section 4, the former section 5 may preferably be formed with inverted taper, preferably at each outer side surface of each of the core elements 50 and 5b.

An example of the core unit 1 has the following main dimensions:

overall length: 480 mm; overall height: 410 mm; overall width: 240 mm; height of section 3: 230 mm; out side dia. of each of projections 2: 74 mm; center-to-center distance between two neighboring cylinders: -120 mm; bore of each cylinder of casting ca 74 mm.

The blow-in and baking steps were completed within 90 seconds.

Finally, the pattern assembly was opened and the formed and baked core were taken out from the pattern assembly. These pattern-opening and core removal steps were completed within 30 seconds.

Although not specifically shown, the core section 5 is formed preferably with inverted tapers, especially at the outer side surfaces of the core elements 5a and 5b, so as to effectively prevent otherwise possible disengagement of the section 5 from its embedded and baked-up position from its mating main body section 3 during a casting step of the metal product, or during handling and transporting operation of the core unit I.

It will be seen that the thus prepared core unit 1 represents no disadvantageous idle gaps between the sections 3 and S by virtue of the tight and rigid baked combination therebetween, and thus a highly reliable, precise and substantially permanent fixture of the bearingforrning section 5 with the main section 3. It is also highly advantageous to prevent casting fins to develop on te molded castings prepared by use of the core unit l in combination with a mating main mold, not shown.

In the foregoing description, the composite core unit 1 and its manufacturing pattern assembly were directed to those which concern with a common cylinder cover of an internal combustion engine, but the invention is not limited only thereto, and can find its broad use in other and various purposes The embodiments of the invention in which an exclusive property of privilege is claimed are as follows:

1. A composite core for molding a common cylinder cover casting of a multi-cylinder internal combustion engine said composite core comprising a larger main core and at least a smaller auxiliary core section with said smaller core section embedded in said larger core section and securely united thereto in a cast-in and baked manner said larger core section being a main core section including a hollow and lower crankcaseforrning part and an upper multi-cylinder-forming hollow core block made integral therewith and said smaller core section being an intermediate bearingforming core comprising two substantially symmetrical core elements pre-shaped and baked, said elements being rigidly united together by bringing partition surfaces formed thereon into glued engagement with each other. 

1. A composite core for molding a common cylinder cover casting of a multi-cylinder internal combustion engine said composite core comprising a larger main core and at least a smaller auxiliary core section with said smaller core section embedded in said larger core section and securely united thereto in a cast-in and baked manner said larger core section being a main core section including a hollow and lower crankcase-forming part and an upper multi-cylinder-forming hollow core block made integral therewith and said smaller core section being an intermediate bearing-forming core comprising two substantially symmetrical core elements pre-shaped and baked, said elements being rigidly united together by bringing partition surfaces formed thereon into glued engagement with each other. 